How to use the wind chill calculator
- Enter the air temperature and choose Fahrenheit or Celsius.
- Enter the wind speed and choose miles per hour or kilometers per hour.
- Read the wind chill, the unrounded value and how many degrees colder than the air it feels.
- Use the table to see the same temperature at other wind speeds.
Formula
Wind chill (F) = 35.74 + 0.6215 T - 35.75 V^0.16 + 0.4275 T V^0.16
T = air temperature in degrees F, V = wind speed in mph
Valid only for T at or below 50 F and V above 3 mph
F = C x 9/5 + 32; 1 mph = 1.609344 km/h
This is the formula published by the National Weather Service. Inputs in Celsius or km/h are converted first, and the result is converted back.
Worked example
At 20 F with a 15 mph wind, the wind chill is 35.74 + 12.43 - 35.75 x 15^0.16 + 0.4275 x 20 x 15^0.16 = 6.22 F, which weather services report as 6 F.
At -10 F with 25 mph, it is -37.46 F. At 32 F with 10 mph, it is 23.73 F. The tool refuses a temperature above 50 F or a wind of 3 mph or less, because the formula is not valid there.
What wind chill measures
Wind chill is an index of how quickly exposed skin loses heat in moving cold air. Moving air carries away the thin layer of warm air next to your skin, so you feel colder than the thermometer shows. It does not lower the real air temperature, and objects such as a car or a pipe do not cool below the air temperature because of wind.
Valid range
The National Weather Service states that the formula applies at or below 50 degrees F and for winds above 3 mph. Outside that range, this calculator gives an error instead of a number. Source: https://www.weather.gov/safety/cold-wind-chill-chart. In warm, humid weather other indexes, such as heat index, apply, and in still air the temperature is the better guide.
Using the number
Clothing, sun, wet skin, activity and how long you are outside change how you feel, so use the value as a guide for dressing and for limiting exposure, not as a precise measure. For humidity, see the dew point calculator, and for other conversions use the unit converter.
Assumptions and limits
- The formula, limits and the whole degree rounding follow the National Weather Service wind chill chart, fetched for this page.
- Wind speed is measured at the standard height used for the index, not in a sheltered spot.
- The tool does not estimate frostbite time or risk, which depends on more than the index.
- Temperatures in Celsius are converted to Fahrenheit for the calculation.
Frequently asked questions
How do you calculate wind chill?
Use the National Weather Service formula with the temperature in degrees F and wind in mph: 35.74 + 0.6215T - 35.75 V^0.16 + 0.4275 T V^0.16.
Why can I not calculate wind chill above 50 F?
The formula is only valid at or below 50 F and for winds above 3 mph. At warmer temperatures the cooling effect on skin is not described by this index.
Does wind chill change the actual temperature?
No. It describes how cold exposed skin feels. Inanimate objects only cool to the air temperature, no matter how strong the wind.
What is the wind chill at 20 F with a 15 mph wind?
About 6 F. The unrounded value is 6.22 F.